The present invention relates to a radiation imaging apparatus, and particularly to a radiation imaging apparatus which scans a subject with radiation to acquire projection data and reconstructs the acquired projection data to generate an image of the subject.
A radiation imaging apparatus such as an X-ray CT (Computed Tomography) apparatus moves a subject to an imaging space and scans the subject moved into the imaging space with radiation to acquire projection data of the subject and generates an image about a tomographic plane of the subject on the basis of the acquired projection data. The X-ray CT apparatus has been utilized for a wide range of uses such as a medical use, an industrial use, etc.
In the X-ray CT apparatus, a table section supports the subject and a table moving section moves the table section to an imaging or photographing space. A scan section scans the subject moved to the imaging space by the table moving section and supported by the table section. In the X-ray CT apparatus, an X-ray tube and an X-ray detector are rotated with the direction of a body axis of the subject as the center. The X-ray tube applies X rays from the periphery of the subject along a plurality of view directions. The X-ray detector acquires projection data corresponding to the respective view directions as projection data. Further, the X-ray CT apparatus reconstructs and generates an image about a tomographic plane of the subject on the basis of the projection data from the respective view directions (refer to, for example, a patent document 1).
[Patent Document 1] Japanese Unexamined Patent Publication No. Hei 8(1996)-336526
There is a case in which upon imaging the subject using the X-ray CT apparatus, a contrast agent is administrated in the subject to execute its imaging.
When the contrast agent is administrated in the subject to carry out its imaging, the table moving section moves the table section so as to correspond to the state of progress or traveling of the contrast agent in the subject. In this case, the state of traveling of the contrast agent in the subject is estimated and the table section is moved such that its position is shifted at a constant speed. Therefore, there was a case in which each image of the subject based on the contrast agent could not imaged or photographed without coincidence thereof with the speed of the contrast agent that travels in the blood vessels of the subject.
When the contrast agent is administrated in the subject to carry out its imaging, images about an axial plane vertical to the body axial direction of the subject are displayed in real time in association with a plurality of slice positions. An operator is caused to recognize the state of progress of the contrast agent. Therefore, when the contrast agent travels in the direction along the body axial direction as in a foot part of the subject, it is difficult for the operator to recognize the state of progress of the contras agent. There is a case in which it is difficult to confirm whether imaging is done corresponding to the state of progress of the contrast agent.
Thus, the radiation imaging apparatus such as the X-ray CT apparatus does not have sufficient operability when the contrast agent is administrated in the subject to carry out its imaging, and encounters difficulties in carrying out the imaging efficiently.
The present invention relates to a radiation CT system such as an X-ray CT system, a data acquisition system, and a data acquisition method.
Radiation CT systems employing a multi-array detector that has a plurality of detector elements set in array in a direction of channels and in a direction of slices alike are known (refer to, for example, Patent Document 1). Output signals of the detector elements are amplified by amplifiers included in a data acquisition system (DAS). In general, the number of amplifiers is the same as the number of detector elements (the number of channels by the number of arrays juxtaposed in the direction of slices).
Patent Document 1 describes that four data acquisition systems (DASs) are used in combination with a multi-array detector having eight arrays of detector elements juxtaposed in the direction of slices, that the connections between the arrays of detector elements and the data acquisition systems are changed based on a slice thickness, and that one amplifier amplifies outputs of two arrays of detector elements. Herein, the connections are changed from ones to others prior to scanning, and two arrays of detector elements are treated as one array of detector elements. This is equivalent to a case where the same number of amplifiers as the number of detector elements is included.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2001-212128
As for a multi-array detector, an increase in the number of arrays of detector elements juxtaposed in the direction of slices or realization of finer detector elements, that is, an increase in the number of detector elements is demanded from the viewpoint of a shorter scan time or improved image quality. On the other hand, amplifiers are included in a data acquisition system in association with all detector elements. The number of amplifiers increases along with an increase in the number of detector elements, whereby various drawbacks take place. For example, it is hard to preserve a space in which the amplifiers are disposed, a power consumption increases, an amount of dissipated heat increases, and a cost increases.